At present, communication systems provide application or services for individual users and/or group users, and communication media employed in these services may include text, audio, video, and varieties combinations of multimedia. An ordinary application or service is mainly oriented to individuals, and usually there is only one or two User Equipments (UEs) communicate with each other in such an application or service. However, in an application or service in which group users take part, users of one or more groups usually communicate with other users simultaneously. In other words, this kind of communication is not a two-party communication including one calling user and one called user, but a communication including a plurality of calling users and a plurality of called users. Such an application or service in which group users take part is also called a multi-party service.
In a session-based service, a Charging Identifier (CID) is allocated each time when an Application Server (AS) establishes a session with a UE, and all CIDs allocated are saved in the AS and a service bearer network. A billing center obtains Charging Data Records (CDRs) corresponding to the CIDs from the service bearer network and the AS via a charging function collecting entity, and combines the CDRs corresponding to a same CID for charging. For application or services employing an IP Multi-media Subsystem (IMS) as a service bearer network, the CIDs allocated are also called IMS Charging Identifiers (ICIDs). However, the inventor of this application finds out that the CID-based charging method described above can not meet the requirements of practical applications.
For example, in a service communication, when a UE establishes a session for a first time with an AS, the UE is given a CID. For some reasons, the UE exits the service communication temporarily before the service communication is ended. Later, the UE re-enters the service communication. In such a case the UE is given a new CID for a session established after re-entering the service communication. From a perspective of a user using the UE, the two sessions, established for the first entering and established for the re-entering respectively, are two related sessions, and need to be combined for a charging. However, from a perspective of the billing center, the two sessions correspond to different CIDs, thus the two sessions are considered as unrelated sessions. If the two sessions need to be correlated, the billing center needs to analyze CDRs of the two sessions and perform complicated calculation based on user information in the CDRs, yet it is still difficult to guarantee an accurate correlation of the two sessions. Such problem is more apparent in multi-party services.
In a multi-party service, UEs used by users of various parties of this service access a center control server via respective access server. The center control server provides centralized session handling, which includes session signaling control, media transmission authorization to communication parties, media data replication and distribution. One multi-party service has one center control server and at least one access server. The center control server performs controlling function (CF) and the access server performs participating function (PF). Logically, a CF corresponds to a multi-party service. In a multi-party service, the CF establishes one session for each UE, and each of the sessions corresponds to a PF. Therefore, the center control server performs a CF while the access server performs at least one PF corresponding to at least one UE connected to the access server.
Therefore, multi-party services have a common feature that, a multi-party service has at least one session and each session corresponds to a UE of one user and a CID. Due to such feature of multi-party services, the billing center needs to correlate a great number of CIDs when charging, which leads to poor charging accurate and difficult implementation. Moreover, for a multi-party service, there is also a need to charge a user by correlating a plurality of sessions of the user in one multi-party service. However, according to the charging technique of the prior art, the billing center needs to generate CDRs based on ICIDs first and make further calculations based on group information in the CDRs, which is still complicated and tends to be inaccurate.
As discussed above, CID-based charging method in the prior art cannot correlate different sessions of a user in one service communication, but only actions of the user in one session. Such charging method may easily charge twice for one action or leave an action uncharged, which threatens security and reliability of charging operations and reduces user satisfaction.
Furthermore, as new demands emerges, it is becoming more and more difficult for one AS to handle a plurality of application or services. Operators or service providers are developing multi-services including a plurality of sub-services, in order to provide more flexible and richer services. Relative to the multi-services, the above applications services provided by the AS may be called single-services. In a multi-service, each sub-service has a sub-service server e.g. an AS. A whole multi-service has a service control function adapted to control all sub-service servers in a manner, for example, the service control function controls initiation procedures of sub-services and controls assignment of sub-service session identifiers. A typical multi-service includes a sub-service regarded as a primary service, and all other sub-services of the multi-service are regarded as supplementary services. The sub-service server of the primary service may be called a primary service server and the sub-service servers of the supplementary services may be called supplementary service servers. The supplementary services rely on the primary service to some extent and provide supplementary functions for the primary service. For example, a Presence Server may be set in a PoC service network and be used to display group status to users during a PoC service. For another example, a Location Service Server (LCS Server) may also be set in a PoC service network to provide location information of participating users.
Along with the developing of multi-services, operators or service providers may develop charging policies for multi-services. However, as discussed in the preceding description, the conventional charging method is based on CIDs corresponding to separate sessions. Therefore the billing center needs to correlate CDRs of a plurality of services in a multi-service charging. Because a CID corresponds to only one session of a sub-service of a user, the billing center needs to analyze each CDR and perform comprehensive calculation with complicated processes, which leads to low charging accuracy and low feasibility.
Therefore, the conventional CID-based charging method is just applicable to correlating a plurality of actions of a user in one session, but is not applicable to correlating a plurality of sessions of a user in a single-service or and cannot correlate a plurality of sessions of a user in a plurality of sub-services of a multi-service.